1. Technical Field
The present invention relates to a coil to be used as an electronic component and a method for forming the coil and more particularly to the coil suitably used as a coil of a reactor and the method for forming the coil.
2. Description of Related Art
In general, a reactor has, for example, a winding and a core made of a magnetic substance and the winding is wound around the core to make up the coil of the reactor, which enables inductance to be obtained. Conventionally, the reactor is used in a voltage boosting circuit, inverter circuit, active filter circuit, or the like, and, in many cases, such the reactor has a structure in which the core and the coil wound around the core are housed, together with other insulating members or the like in a case made of metal or the like (see, for example, Patent Reference 1).
For a reactor to be used in a vehicle-mounted voltage boosting circuit, a coil is used which has a structure in which two single-coil elements each having a predetermined winding diameter and the number of windings that can provide a high inductance value in a high current region are formed in parallel to each other and are coupled (connected) to each other so that the directions of currents flowing through both the coils are reversed to one another.
The first conventional example of such the coil has a structure in which each of the two single-coil elements described above is formed by individual winding and the two single-coil elements are connected to each other by performing welding on an end portion on the coupling side of the windings via communicating terminals (see, for example, Patent Reference 2).
The second conventional example of such the coil has a structure in which two single-coil elements placed in parallel to each other and wound in the same direction are formed by edgewise winding using one piece of rectangular wire rod and the resulting coil is housed within the outside shape formed by end surfaces of both the coil elements by folding, in half, the coupling portion of the rectangular wire rod lying between the above two single-coil elements connected to each other along a width direction orthogonal to a longitudinal direction (see, above Patent Reference 2).    Patent Reference 1: Japanese Patent Application Laid-open No. 2003-124039    Patent Reference 2: Japanese Patent No. 3737461